Effect of plasticity of the cladding with different thicknesses on the bearing capacity of the brittle base wall of RPV under PTS loads.

In the research field of reactor pressure vessel (RPV) subjected to pressurized thermal shock (PTS), the traditional linear elastic analytical method generally ignores the plastic properties of cladding. In fact, the neutron irradiation in RPV is easy to cause the embrittlement of the base material rather than cladding. So the elastic-plastic parameters of cladding are introduced into the FE model of the RPV with a sub-clad crack. The stress distributions in the thermal-mechanical coupling fields related to the base wall and cladding of different thicknesses are then obtained. The XFEM is used to simulate the crack growth in the nozzle area. The allowable internal pressure in the dangerous moment of the PTS is calculated to show the ultimate bearing capacity of the structure. The numerical results are compared with those only considering the elasticity of cladding. Furthermore, the law of the effect of plasticity of cladding on the structural safety is summarized.